virtual domains and mailman with Postfix

[Russell Coker <russell@coker.com.au>]

In main.cf I have:
virtual_maps = hash:/etc/postfix/virtual

In /etc/postfix/virtual I have the following:
# mailman
lists.example.com               virtual
mailman-owner@lists.example.com example-listowner
testing@lists.example.com               list-testing
testing-admin@lists.example.com list-testing-admin
testing-request@lists.example.com       list-testing-request
testing-owner@lists.example.com list-testing-admin
@lists.example.com                      example-listowner

In /etc/aliases I have:
# mailman
example-listowner: rop, etbe
## testing mailing list
## created: 09-Sep-2002 root
list-testing:             "|/var/lib/mailman/mail/wrapper post testing"
list-testing-admin:       "|/var/lib/mailman/mail/wrapper mailowner testing"
list-testing-request:     "|/var/lib/mailman/mail/wrapper mailcmd testing"
#list-testing-owner:       testing-admin

Now when I send mail from the local machine it all works as expected (I send 
mail to testing-request@lists.example.com with subject "help" and I get the 
help message).  But if I send mail from outside the network I get the 
following:
<testing-request@server.example.com>: mail for server.example.com loops back 
to myself

Now lists.example.com is a CNAME pointing to server.example.com.

So why is mail sent from the local machine with mailx working, while a message 
sent on port 25 with the same content is rejected?

-- 
I do not get viruses because I do not use MS software.
If you use Outlook then please do not put my email address in your
address-book so that WHEN you get a virus it won't use my address in the
>From field.